A must have for any s&w m&p series gun. - Crimson Trace M&P Full-Size Rear Activation Laser Pistol Grip

A fantastic product. Super simple to setup: install a battery in the grip, swap the M&P back strap with the CT grip, and adjust the elevation and windage using a hex key.
To activate, grasp the firearm as you would normally do, and the laser automatically comes on.
Pros: Super simple, just grip your gun and the beam is on.
Cons: A bit pricey. Putting your finger outside of the trigger guard may block the beam.

This review was written in the old system and had content requirements that are different than reviews written today.